Oxford English Dictionary Ecology. [etymology: < ancient Greek house, dwelling]
1.a. The branch of biology that deals with the relationships between living organisms and their environment. Also: the relationships themselves, esp. those of a specified organism.
b. Chiefly Sociological. The study of the relationships between people, social groups, and their environment; (also) the system of such relationships in an area of human settlement. Freq. with modifying word, as cultural ecology, social ecology, urban ecology.
2. The study of or concern for the effect of human activity on the environment; advocacy of restrictions on industrial and agricultural development as a political movement; (also) a political movement dedicated to this.